Fireshield fastener hood

ABSTRACT

A fireshield fastener hood and method of bonding a cover to a substrate therefor.

RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/168,195 filed on Jun. 24, 2011, the entirety of which is hereinincorporated by reference.

BACKGROUND

The present disclosure relates to a fireshield, and more particularly toan aircraft nacelle fireshield.

Fireshields often line sections of gas turbine engine nacelle structuressuch as thrust reverse sections to provide thermal protection.Fireshields are subject to high temperatures and eventually may requirereplacement.

Fireseal fastener hoods are welded thermal protection covers forfasteners and fastener holes by which the fireshield is attached toengine nacelle structure. Fireseal fastener hoods typically extendoutward from the fireshield and may be particular susceptible tohandling damage which in turn may necessitate replacement of the entirefireshield because welding a replacement hood may damage an underlyingsubstrate.

SUMMARY

A method of repairing a fireshield fastener hood according to anexemplary aspect of the present disclosure includes bonding a cover to asubstrate.

A fireshield fastener hood according to an exemplary aspect of thepresent disclosure includes a cover bonded to a substrate.

A fireshield according to an exemplary aspect of the present disclosureincludes a fireshield fastener hood welded to a fireshield at a hinge,the fireshield fastener hood includes a cover bonded to a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a general perspective view of part of a nacelle structure fora gas turbine engine embodiment for use with the present disclosure;

FIG. 2 is an exploded view of a fireshield of the nacelle structure ofFIG. 1;

FIG. 3 is an inner view of the fireshield illustrating a fireshieldfastener hood

FIG. 4 is a sectional view of the fireshield fastener hood attached to afireshield mounted to the nacelle cowl;

FIG. 5 is a sectional view of the fireshield fastener hood;

FIG. 6 is a perspective view of the fireshield fastener hood;

FIG. 7 is a schematic view of an allowable crack area in the fireshieldfastener hood for a repair thereof;

FIG. 8 is a method of repair steps for the fireshield fastener hood;

FIG. 9 is a perspective view of the fireshield fastener hood with a tabcut off;

FIG. 10 is a sectional view of the fireshield fastener hood with the tabcut off;

FIG. 11 is a perspective view of the fireshield fastener hood with acover mounted thereon;

FIG. 12 is a sectional view of the fireshield fastener hood with a covermounted thereon;

FIG. 13 is a sectional view of a replacement tab taken along line 13-13in FIG. 11;

FIG. 14 is an edge view of the fireshield fastener hood with a coveralong line 14-14 in FIG. 11; and

FIG. 15 is a top view of the fireshield fastener hood with the cover.

DETAILED DESCRIPTION

FIG. 1 illustrates a Thrust Reverser Core Cowl portion of a gas turbineengine nacelle structure 20. Although a nacelle structure 20 isillustrated in the disclosed non-limiting embodiment, it should beunderstood that various structures will benefit herefrom and thedisclosure herein should not be limited only to such structures.

With reference to FIG. 2, the nacelle structure 20 generally includes aninner cowl section 24 onto which is mounted a fireshield 26. The cowlsection 24 is typically manufactured from a carbon fiber or light weightmetallic material such as an aluminum alloy which may require thethermal protection of the fireshield 26 during normal service or in theabnormal event of a fire in that compartment.

The fireshield 26 is mounted to a multiple of studs 28 which extend fromthe cowl section 24. The studs 28 extend through the fireshield 26 toreceive a fastener 30 such as a nut to retain the fireshield 26 to thecowl section 24. The extended stud 28 and fastener 30 are protected by amovable fireshield fastener hood 32 (FIG. 3). Although a movablefireshield hood for a fastener is discussed in detail herein, it shouldbe understood that other fireshield hoods such as that for a hinge 34will also benefit herefrom.

With reference to FIG. 4, the fireshield fastener hood 32 generallyincludes a frustro-conical hood 36 which extends from a generally planarplatform 38 which includes a tab 40 and a bendable hinge 42 (alsoillustrated in FIG. 5). The hood 36, platform 38, tab 40 and hinge 42may be manufactured of an AISI 300 Series Stainless Steel alloysubstrate 44 which is approximately 0.003 inches (0.0762 mm) thick. Asilicone layer 46 coats the interior of the hood 36 and apolytetrafluoroethylene disk 48 is mounted to the apex of the hood 36 toprotect the silicone layer 46 should the relatively thin substrate 44 beover-compressed to make intimate contact with the stud 28. It should beunderstood that various other constructions may alternatively oradditionally be provided and the fireshield fastener hood 32 may be ofvarious geometries.

The hinge 42 is a folded section of the substrate 44 which may be tackwelded to the fireshield 26 to permit the fireshield fastener hood 32 tomove relative thereto. The tab 40 extends from the platform 38 forreceipt into a retainer 50 in the fireshield 26 to close the fireshieldfastener hood 32 over the stud 28 and fastener 30. To access the stud 28and fastener 30, the tab 40 is slipped out from under the retainer 50and the fireshield fastener hood 32 is pivoted upon the hinge 42.

Oftentimes the substrate 44 may crack, tear, or otherwise be damaged ina manner which is repairable by the method disclosed herein (FIG. 6).Typically, acceptable cracks may be located in an arc of approximately170 degrees from the center of the hood 36 in an area adjacent to thetab 40 (FIG. 7). It should be understood that other crack locations mayalternatively or additionally allowable.

With Reference to FIG. 8, step 100 of a manufacture or repair to thefireshield fastener hood 32 includes cleaning the repair area of thefireshield fastener hood 32. The cleaning facilitates bonding and crackinspection. The repair to the fireshield fastener hood 32 may beperformed while the fireshield fastener hood 32 is mounted to thefireshield 26 (FIG. 3).

Step 102 of the repair may include removal of the tab 40 (FIGS. 9 and10). The tab 40 may be trimmed to be from 0 to 0.3 inches (0-8 mm) fromthe platform 38. The tab removal may only be necessary where an extrathick tab 40 will not fit under retainer 50 or when tab 40 is damaged.

With Reference to FIG. 11, a cover 52 is formed to match the contour ofthe substrate 44, hood 36 and platform 38 (Step 104). The cover 52 maybe formed over a rigid tool which is generally of the contour of thehood 36 and the platform 38. It should be understood that a kit toperform the repair may include a preformed cover 52. The cover 52 shouldcover the entire contoured hood surface with sufficient material toallow trim. Folds and wrinkles are permitted, but the cover 52 must nothave any cracks or tears.

The cover 52 may be manufactured of an AISI 300 Series Stainless Steelalloy which is approximately the same thickness as the hood 32. That is,the cover 52 may be manufactured from a similar material as thesubstrate 44. The cover 52 may also form a replacement tab 40′. That is,the cover 52 forms a double layer of material over the hood 36 and theplatform 38 but a single layer to define the replacement tab 40′ as onlya single layer thickness would fit within the retainer 50 (FIG. 12). Thesection of the cover 52 which forms the replacement tab 40′ should bedoubled over a minimum of 0.08 inches (2 mm) along the length of thereplacement tab 40 to increase the strength to the replacement tab 40′(FIG. 13).

Step 108 of the repair includes trimming the cover 52 to cover thesubstrate except the hinge 42. The trimming should include additionalmaterial to wrap around the edges. (FIG. 14). The cover 52 may be amaximum of 0.060 inches (10 mm) of the edge (FIG. 14). It is permissibleto trim the replacement tab 40′ of the cover 52 to width and lengthafter bonding.

In step 110 the cover 52 is cleaned.

In step 112, a layer of primer 54 is applied to the mating surface ofthe cover 52, and the substrate 44. The primer 54 may be a siliconeprimer compatible with the fire wall sealant 56, such as DAPCO 1-100manufactured by D Aircraft Products Inc. of California, USA.

With reference to FIG. 12, in step 114, a layer of sealant 56 is appliedto the mating surface of the cover 52, and the substrate 44. The sealant56 may be a thixotropic silicone paste firewall sealant such as DAPCO18-4F manufactured by D Aircraft Products Inc. of California, USA.

In step 116, the cover 52 is then pressed onto the layer of sealant 56on the substrate 44. The cover 52 is wrapped over the edges of thesubstrate 44 (FIG. 14). It is permissible to dart the cover 52 at theedges where the cover 52 extends beyond the hood 36 before the edges arefolded over the platform 38. A Radius of 0.06-0.25 inches (1.5-6.35 mm)may be formed between the platform 38 and the replacement tab 40′ (FIG.15). The radius also minimizes stress concentrations.

In step 118, excess sealant is removed before curing cycle (Step 122).

In step 120, the cover 52 is edge sealed (step 120). Sealant squeeze outis required all around the cover 52 (FIG. 14). The cover 52 is wrappedaround the edge to a minimum of 0.2 inches (5 mm) and edge sealed in thesealant 56 (FIG. 14). The perimeter is to be fully encapsulated.

In step 122, the sealant 56 is cured.

In step 124, the cover 52 is inspected for complete sealing andattachment.

In step 126, the replacement tab 40′ is inserted into the retainer 50(FIG. 3).

The repair method covers the damaged area with a new thermal barriercover 52 bonded with the sealant 56. The method allows for large scaleproduction or repair.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A fireshield fastener hood comprising: asubstrate, wherein said substrate is a damaged substrate and includes apartial tab, said partial tab being the result of a portion of saidpartial tab being separated from the remainder of said partial tab; anda cover bonded to said substrate to form a radius between a tab of saidcover and a platform of said substrate, wherein the radius provides arounded corner, when viewed from a top of the cover, between twosubstantially perpendicular edges of the cover.
 2. The fireshieldfastener hood as recited in claim 1, wherein said cover matches acontour of a frustro-conical hood and a planar platform of saidsubstrate.
 3. The fireshield fastener hood as recited in claim 1,wherein said substrate and said cover is formed from an AISI 300 seriesstainless steel.
 4. The fireshield fastener hood as recited in claim 1,wherein said cover is bonded to said substrate with a sealant.
 5. Thefireshield fastener hood as recited in claim 4, wherein said sealant isa thixotropic silicone paste firewall sealant.
 6. A fireshield assemblycomprising: a fireshield; and a fireshield fastener hood welded to saidfireshield, said fireshield fastener hood includes a cover bonded to asubstrate, wherein said substrate is a damaged substrate and includes apartial tab, said partial tab being the result of a portion of saidpartial tab being separated from the remainder of said partial tab, andwherein said cover is bonded to said substrate to form a radius betweena tab of said cover and a platform of said substrate, wherein the radiusprovides a rounded corner, when viewed from a top of the cover, betweentwo substantially perpendicular edges of the cover.
 7. The fireshieldassembly as recited in claim 6, wherein said fireshield defines a slotto receive a tab defined by said cover.
 8. The fireshield assembly asrecited in claim 6, wherein the tab of said cover is doubled over alonga length of the tab of said cover.
 9. The fireshield fastener hood asrecited in claim 8, wherein the tab of said cover is doubled over alongat least a length of 0.08 inches (2 mm) of the tab of said cover. 10.The fireshield assembly as recited in claim 8, wherein the tab of saidcover is doubled over along at least a length of 0.08 inches (2 mm) ofthe tab of said cover.
 11. The fireshield fastener hood as recited inclaim 1, wherein the radius is within a range of 0.06 to 0.25 inches(1.5 to 6.35 mm).
 12. The fireshield assembly as recited in claim 6,wherein the radius is within a range of 0.06 to 0.25 inches (1.5 to 6.35mm).
 13. The fireshield fastener hood as recited in claim 1, whereinsaid partial tab is the result of a crack in a tab of said substrate.14. The fireshield assembly as recited in claim 6, wherein said partialtab is the result of a crack in a tab of said substrate.
 15. Thefireshield fastener hood as recited in claim 1, wherein the tab of saidcover overlaps said partial tab.
 16. The fireshield fastener hood asrecited in claim 15, wherein the tab of said cover projects further fromsaid platform than said partial tab.